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Did anyone else read this and immediately wonder, "how many watts?" 1.5 pages of prose and no hard numbers. Years in the industry reading marketing white papers

by iyulaev 13y ago

Did anyone else read this and immediately wonder, "how many watts?" 1.5 pages of prose and no hard numbers. Years in the industry reading marketing white papers and such cause things like this to really set off the bullshit detector. I'm not saying it's not possible, but, just give me the power (in watts) that is being transmitted by a prototype device. If you don't put that number as a feature bullet, I automatically assume you've got something to hide.

cma 13y ago
I was wondering about the watts for a different reason... From Wikipedia: "Although the long term effects due to ultrasound exposure at diagnostic intensity are still unknown,[24] currently most doctors feel that the benefits to patients outweigh the risks.[25] The ALARA (As Low As Reasonably Achievable) principle has been advocated for an ultrasound examination — that is, keeping the scanning time and power settings as low as possible but consistent with diagnostic imaging — and that by that principle non-medical uses, which by definition are not necessary, are actively discouraged."
- VLM 13y ago
  I would imagine the doppler effects of beaming a couple watts at a low freq thru a ceiling fan would be humorous. Another interesting one is phase noise and distortion and crossover distortion (if you use a simple class-B amp) means you can send a sine wave into a high power amp, but the amplified noise level at audible range might be icky. As a personal anecdote I've noticed this with commercial ultrasonic cleaners. Sure... noise level might be 30 dB down at audible range, but pump a 100 watts at 40 KHz into it and I'm listening to 0.1 watts of noise at audible freqs which is quite loud indeed. Theoretically ultrasonic cleaners should be inaudible, but high powered ones are not. Much as intermod distortion is hilarious with high power RF, noisy/corroded/semi-faulty ultrasound could be loud as heck acoustically thru no fault of the generator, amp, or transducer.
  - iyulaev 13y ago
    Did not consider this. Intermodulation and other distortion by-products are going to be difficult to control although I have no experience with the performance of modern amps for sub-MHz frequency ranges. Building a working prototype that can beam ~1W (or even 100mW) a few feet would be very interesting and would do a lot to lessen my skepticism.

by iyulaev 13y ago

cma 13y ago

I was wondering about the watts for a different reason... From Wikipedia: "Although the long term effects due to ultrasound exposure at diagnostic intensity are still unknown,[24] currently most doctors feel that the benefits to patients outweigh the risks.[25] The ALARA (As Low As Reasonably Achievable) principle has been advocated for an ultrasound examination — that is, keeping the scanning time and power settings as low as possible but consistent with diagnostic imaging — and that by that principle non-medical uses, which by definition are not necessary, are actively discouraged."

VLM 13y ago
I would imagine the doppler effects of beaming a couple watts at a low freq thru a ceiling fan would be humorous. Another interesting one is phase noise and distortion and crossover distortion (if you use a simple class-B amp) means you can send a sine wave into a high power amp, but the amplified noise level at audible range might be icky. As a personal anecdote I've noticed this with commercial ultrasonic cleaners. Sure... noise level might be 30 dB down at audible range, but pump a 100 watts at 40 KHz into it and I'm listening to 0.1 watts of noise at audible freqs which is quite loud indeed. Theoretically ultrasonic cleaners should be inaudible, but high powered ones are not. Much as intermod distortion is hilarious with high power RF, noisy/corroded/semi-faulty ultrasound could be loud as heck acoustically thru no fault of the generator, amp, or transducer.
- iyulaev 13y ago
  Did not consider this. Intermodulation and other distortion by-products are going to be difficult to control although I have no experience with the performance of modern amps for sub-MHz frequency ranges. Building a working prototype that can beam ~1W (or even 100mW) a few feet would be very interesting and would do a lot to lessen my skepticism.